Salinity is a key factor limiting plant growth and development. While the potential of hydrogen as a gaseous signaling molecule in enhancing crop salt tolerance has been recognized, the molecular mechanisms regulating crop growth and defense remain poorly understood. This research explores this issue via the comprehensive transcriptomic and metabolomic analysis of pakchoi ( Brassica chinensis L.) under co-exposure to NaCl and hydrogen nanobubbles (HNBs). The results demonstrated that compared to the control, salt treatment significantly upregulated the synthesis and/or transduction pathways of stress hormones (ABA, JA, ET) as well as the phenylpropanoid biosynthesis pathway. This was accompanied by increased antioxidant enzyme activity and total phenolic content but also resulted in plant growth inhibition, stomatal closure, and elevated ROS content. However, compared to salt treatment, HNBs treatment partially attenuated the expression of hormone-related signaling components and reduced the content of defensive secondary metabolites (total phenolics), while further enhancing antioxidant enzyme (SOD, CAT, APX) activities and soluble sugar content. These changes were consistent with reduced ROS levels, improved stomatal aperture, and alleviated growth inhibition. These results indicate that HNBs stimulation may optimize the growth-defense balance in pakchoi under salt stress rather than sacrificing growth to adapt to the stress, which highlights the potential of HNBs in advancing sustainable agricultural practices. • HNBs confer pakchoi tolerance to salt stress. • HNBs suppress salt-induced over-activation of ABA, JA, and ET signaling pathways. • HNBs sustain stomatal opening and lower ROS in salt-stressed pakchoi. • HNBs enhance SOD, CAT, and APX activities and reduce defensive phenolic synthesis.
Guo et al. (Fri,) studied this question.